The following description provides a summary of information and is not an admission that any of the information provided or publications referenced herein is prior art to the present application.
Nonalcoholic fatty liver disease (NAFLD) is defined as the presence of hepatic steatosis, with or without inflammation and fibrosis, in the absence of alcohol history. NAFLD is subdivided into nonalcoholic fatty liver (NAFL) and nonalcoholic steatohepatitis (NASH). In NAFL, hepatic steatosis is present without evidence of significant inflammation, whereas in NASH, hepatic steatosis is associated with hepatic inflammation that may be histologically indistinguishable from alcoholic steatohepatitis.
NAFLD has become an epidemic worldwide and is the leading cause of liver disease in North America, as a result of the rapidly increasing prevalence of obesity. However, accurate population-based data on the incidence of NAFL and NASH are sparse, in part because the diagnosis requires histopathologic documentation. Major risk factors for NAFLD are central obesity, type 2 diabetes mellitus, high levels of triglyceride (fat) in the blood, and high blood pressure. In the U.S., NAFLD is present in 20-40% of the population and NASH is present in about 25% of the obese population. Ten to twenty-nine percent of the NASH patients develop cirrhosis and 4-27% of those develop hepatic cancer.
Most people with NASH have no symptoms. Some may have right upper quadrant pain, hepatomegaly, or nonspecific symptoms such as abdominal discomfort, weakness, fatigue or malaise. A doctor or nurse may suspect the presence of NASH from the results of routine blood tests. In NAFLD, liver enzymes aspartate aminotransferase (AST) and alanine aminotransferase (ALT) are often high.
The current gold standard to confirm NASH is a histological evaluation of liver biopsy, which is expensive, invasive, and can cause pain, hemorrhage, or even death.
A simple blood test that would identify and distinguish the various stages of both NAFLD and NASH (and thereby reduce the need for liver biopsy) would be highly desirable.